1. Field of the Invention
This invention relates to a method of enclosing a substrate using a heat recoverable article and a curable adhesive and to a heat recoverable article having a curable adhesive on a surface thereof.
2. Introduction to the Invention
Many methods are known for joining, repairing, protecting, reinforcing and otherwise modifying pipes and other substrates. In some of those methods, an insert, composed of a polymeric material which can be deformed under heat and pressure, is placed between the substrate and a heat-recoverable article. When heat is applied, the article recovers toward the substrate, and the insert softens and bonds the recovered article to the substrate. Typically heat is applied by means of a torch, air gun, oven or the like. More recently, devices have been developed in which heat recoverable articles are recovered by electrically heating the article by passing electrical current through the article or a conductor embedded in or adjacent the article. Reference may be made for example to U.S. Pat. Nos. 4,085,286 (Horsma et al), 4,177,446 (Diaz), 4,421,582 (Horsma et al), 4,775,501 (Rosenzweig), 4,853,165 (Rosenzweig), and 4,944,987 (Cordia et al), to European Patent Application Nos. 173,541 (Becker et al) and 307,197 (Gansbuehler), and U.K. Patent No. 1,265,194 (Cook), the disclosures of which are incorporated herein by reference.
Typically, the insert comprises a thermoplastic hot melt adhesive, e.g. a thermosetting adhesive. The use of thermosetting adhesives is disclosed in U.S. Pat. Nos. 4,707,388 (Park et al), 4,729,920 (McLoughlin et al), 4,798,752 (McLoughlin et al), 4,844,959 (Read et al) and 4,935,270 (Read et al), and European published patent applications Nos. 117,736 (Pithouse et al), 117,737 (Harris et al), 152,213 (Cordia et al) and 281,354 (Park et al), and International patent application No. WO84/04320 (Senior et al). The reactive components of these thermosetting resin adhesives generally are maintained apart from one another, for example, as particles or fibers, or require an accelerator which is applied to the substrate or otherwise brought into contact with the thermosetting resin at the time it is installed. These articles perform very well but are difficult to manufacture and/or have been found to have a relatively short shelf life. Many commercially successful articles are provided with a coating of reactive particles. However, special care must be taken during manufacture, storage and use to prevent the powdered reactive components from flaking off from the backing.
Thermoplastic epoxy adhesives and pre-pregs are also known, for example in U.S. Pat. No. 4,656,208 (Chu et al), Japanese Kokai Nos. 59-36156 (Kubo et al), 62-141083 (Ohmori et al), 62-153349 (Suzue et al), 60-120779 (Miyauchi et al), and 61-81476 (Nishiyama et al), in European patent application No. 373,440 (Weber et al), and in UK Patent Application GB 2207676A (Schmid et al), the disclosures of which are incorporated herein by reference. However, the use of these adhesives and pre-pregs in combination with heat-recoverable articles which shrink fit the adhesives and/or pre-pregs until they bond to and join together pipes and the like is neither suggested nor disclosed by the aforementioned patents.
Prior art polymers which have been used as adhesives and have been bonded to articles, for example pipes, being joined to one another using heat-recovering articles, have generally not been sufficiently non-tacky so as to be easily handled and positioned in place for forming such bonds, have generally not been tough enough to be easily wrapped around facing pipe ends without cracking and have generally not had a desirably long shelf life. In addition, when the two substrates to be joined are of different materials, e.g. when a metal pipe is to be joined to a glass-reinforced pipe, there may be a problem with differential thermal expansion between the substrates and the adhesive, resulting in cracking, voids, and poor bonds.
The present invention is directed to overcoming one or more of the problems as set forth above.